Sinn Féin's tabled the motion after the Tánaiste leaked a confidential GP contract negotiated with the IMO to a rival group of doctors.
Leo Varadkar apologised in the Dáil last week for "errors of judgement".
But Sinn Fein says today's motion is about ending an "insiders club" in Irish politics.
Finance Minister Paschal Donohoe is confident Leo Varadkar will survive tonight's vote:
"I think it's very, very likely that it will be defeated. I think Government TDs and those who work with Leo I think accept two things, the first thing they accept is that the way in which this particular matter was handled fell short of the standards that Leo Varadkar has for himself. But the second thing I think they accept is that Leo has demonstrated the highest of standards in his time in public office."
